The present invention is capable of observing the way of surface treatment in real time with a high-speed scanning probe microscope (SPM) (atomic force microscope(AFM)), and performing fine surface treatment with a probe even using a cantilever having a small spring constant. A treatment device for treating the surface of a sample (4) using the scanning probe microscope (SPM, AFM) comprises: stages (6, 7) on which the sample is mounted; a cantilever (3) which is provided to face the surface of the sample (4); displacement measuring means (1, 2) for measuring the displacement of the cantilever; a surface texture image acquiring means for acquiring a surface texture image of the sample as a result of the measurement of the displacement of the cantilever by the displacement measuring means while varying the relative position between the cantilever and the sample; and a surface treatment means (5) for treating the surface of the sample with the probe by applying external force from a system different from a cantilever system between the surface of the sample and the probe (8) which is provided to the tip of the cantilever. The acquisition of the surface texture image by the surface texture image acquiring means and the surface treatment by the surface treatment means are alternately repeated.